doc: describe modeling steps

[dacoex]

Just to catch your options:

Would the documentation benefit from having a section, mapping the functionality against the typical modelling steps outlined in:
https://pvpmc.sandia.gov/modeling-steps/
https://pvpmc.sandia.gov/wp-content/uploads/2014/08/1199X499_slide2.png

If so, I would embark (slowly) on that.
It would help me and maybe others to understand the library.

Additionally, this would show where functionality is still lacking.

OK, this would be similar to
PV_LIB Version 1_2 Release/html/html/pvlib_functions_by_cat.html
But a bit more semantic and linked.

[wholmgren]

Better linking to PVPMC would be very helpful, but we should avoid duplicating their effort. Better ipython notebook tutorials should be a priority too (see #30). I think we can make the equivalent of pvlib_functions_by_cat.html by modifying the sphinx scripts.

Would be happy to see some PRs for documentation.

[dacoex]

I think we can make the equivalent of pvlib_functions_by_cat.html by modifying the sphinx scripts.

OK. that's it. I will have a look at this someday ;-)

[dacoex]

I think the following will solve this:

• https://github.com/wholmgren/pvlib-python/blob/pvsystem/docs/sphinx/source/package_overview.rst
• any further modelchain documentation